Wormhole
A gas channel is an elongated, hose-like cavity in the weld metal formed by escaping gases during solidification. It usually occurs on heavily contaminated parts and affects tightness and strength.
Physicochemical Mechanism of Action
During the welding process, gases such as hydrogen, carbon dioxide, or nitrogen escape from the metal. These gases form gas bubbles in the heat and can move through the weld metal in elongated shapes if they cannot exchange quickly enough. This leads to the formation of gas channels.
Metallurgical Relevance & Risks in Welding
Gas channels impair the density and strength of the weld metal as they act as pores and do not transmit mechanical loads optimally. They can also lead to hot cracking when the metal is under stress. Furthermore, the escaping gases coarsen the microstructure, which reduces the toughness of the material.
Workshop Practice & Instructions
To avoid gas channels, it is important to thoroughly clean and degas components before welding. If necessary, use a degassing device to remove escaping gases. Also pay attention to the correct welding process and cooling to minimize the formation of gas bubbles. For heavily contaminated components, chemical cleaning or even mechanical polishing is recommended.